Telephone receiver



April 23, 1929. D W; NORWOQD TELEPHONE RECEIVER Filed sept. 24,1925

INVENTOR W Norm/000 ATTORNEY Patented 23, 1929.

DONALD W. Nonwo'on, oF'HoNoLULU, TERRITORY on HAWAII.k

TELEPHONE RECEIVER.

Application filed September 24, 1925. Serial No. 58,342.

This invention relates to ,electrical"receivers such as are used 1n electrical communication, and the primary object is the provision ot a receiver which will be exceedingly thin and yet have improved tone 'characteristics and efiiciency in reproduction ot speech.

My invention utilizes a helical permanent magnet which adjoins the rim of a magnetic diaphragm, a single electrical coily ot large diameter being placed within the per-y manent magnet to cooperate with a soft iron core within the coil. The various parts of the receiver are all arranged .concentri'cally and since all are ot large diameter compared with their depth, an exceedingly thin receivxr is obtained whichy will nevertheless be extremely efficient sincethe energized coil of wire is entirely surrounded by the magnetic flux path. The center ot the diaphragm is `closely adjacentto the center of thesott iron core, the remaining points et the diaphragm being spaced from the adjacent portions ot the core varying distances, depending upon the distance from thecenter so that the magnetic flux acting on any point in the diaphragm is proportional to the displacement desired at that point.` The diaphragm will thus be caused to vibrate throughout its whole surface in a symmetrical manner and without distorting` the signals transmitted. Means is provided so that the .spacing for air gap exist-ing between the diaphragm and the soft iron core may be varied so as to increase or decrease the loudness oi the tone and the speed characteristics. n'

More detailed objects amladvantages of my invention will be more @fully set `torth in the attached speciication, in the claims and in the drawings in which f Fig. 1 is a vertical. central section through the receiver, and

Fig. 2 is a perspective view of the helical magnet utilized.

Referring more particularly to the draw? ings, a lower casing l is provided to contain the various parts of the receiver, this casing being formed oi a lower portion 2 and an end plate 3 threaded thereon by means of 'the threads el in the customary manner, This casing may be made of hard rubber or other insulating material. The'end plate 3 is provided with a central aperture 5 through which sound is transmitted. The.

end plate 8 is provided with a flange 6 which bears against the rim of a circulaimagnetic diaphragm 7, a suitable air space being provided between the `diaphragm and the central portions ot the end plate.

Closely adjacent to the diaphragm is provided a soft iron core 8 in the Yform ot a disk with a laterally projecting end flange 9. The end oi? thisflange is in contact with the lower end ot' a permanent helical magnet l0 herein shown as consistingot a l'ew turns of steel. This magnet is provided at one end thereof with an upper face ll which is in Contact with the outer edge ot the diaphragm throughoutnearly the complete circular extent of the latter. At its other end the permanent magnet, as before stated, is in Contact withthe sott iron core 8, and the diaphragm 'l' is thus energized by the permanent magnet and the diaphragm held slight- Lly concaved inwardly by uniformly distrib-v uted series of flux lines which have their' rgreatest intensity at the center et the d1aphragm. The spacing between the coreand the diaphragm'is so designed with its minimum extent atthe center that the magnetic flux acting on any point in the diaphragm is proportional to the displacement desired at that point.

Placed within the permanent magnet and immediatelyoutside of the body portion ot the soft iron core, so to rest upon the lower rflange 9 thereof, .is a single large di aineter coilol" wireindicated at l2, the two ends of which are connected tothe two binding posts l2 and lil where they are adapted to be connected to an external energizing circuit, The coilwill therefore be entirely .surrrmnded by the lflux path ot the receiver' and since it is iml'nediately outside of and adjacent lto the soft iron core, the variations ot magnetic fiuxin this core, due to changes in the current flowing through the coil, will be produced in an efficient and accurate manner. y

The helical permanent magnet is preferably ot large diameter as' compared with its longitudinal extent as shown in Fig. l, this l longitudinal extent being preferably slightly larger than the final position it obtains when in place within the casing, so that a spring tension will be exerted by it to maintain the parts in place ywithin the casing.

The air gap between the diaphragm and the sott iron core may be varied therefore by screwing'futhe end plateiof the 5'casing/lon!or" oil as desired, such as resulting in thecom pression or releasing,ofl the Ahelicalamagnet.V The space betnv'eeny the variiii'is'turiisotthe magnet may be either left vacant orbeiixlled" with a helical strip of suitable yielding material ot a non-magnetic character, such as.' sponge rubber as indicated at 15.

The' diameter'ofthe varioitsparts, it 'will bey noted, is large compared with. their vertical extent'and the various essential (ele.- A ments of ,the receiver 'a reV all mounted f con'- centrically so that are'ceiver ot very flat .appearance isprovided, thus taking up little space at the side of the wearers head. The varionstlux paths through the variofi portions et theairgap are all'syminetrical1to1' the saine distance in spacing, itrom the axis ot symmetry, rdue to `,the symmetrical arrangement of the parts. Thetlistribution ot' the magnetic flux lines Vgenerated .troinxthe permanent magnet vis pi-actically uniform or symmetrical, since this magnet is inV c losef Contact along 'practicallyitsfentire .surface With'the rim oftlie diaphragm, and in close contactvatlits lower portion With the, 'entire circular ,extent of a tlangeof the soft iron*A core. It desired the helicalmagnet may be replaced by a series otdclosely positionedk vertically extending balance nagnets ai-,r ranged with their longitudinal? axis parallel to the axis of syminetryofthe casing" N I am aware that various other changes maybe made WithoutY departing from the scope. of Vmy invention,the preferred form j of which has been'sliowii herein, by Way. of

i example, and I do notrv desire to have myviiii'- ventionarestricted to the exact form shown and described herein.`

I claim :4

l. In an electrical receiver," an "electro. magnetga diaphragm therefor, and a helical`V permanentv magnet cooperating with i said diaphragm' and. in contact therewith toi-1a substantial distance on the edgeot said diaphragm. y

2. In an electrical receiver, in 'combina tion,anelectromagnet, a. diaphragm thereyfor,.and a compressible'helical permanent.

magnethaw'fing a diameter many times the said corefthe tiux path through all points concentric withkthecenter of the diaphragm being the same and the` intensity ot the iiux 'progressively decreasing as the distance trom'th'e center .of the diaphragmincreases 4.,Infa Vdevice ottheclass described, in

combination, a casing, a coil ot' Wirea. sott,

iron coreftheretoi', ,.a, circular :diaphragm having its center closely adj acent the center ot said core, a permanent magnet interconiiectiiigfsaid diaphragiirat substantially all ot outsideportions witlrtlie said core tliroughp aths otx sulostaiitialiyuniformv rflux resistance, the Asaid .core ,magnet anddiaphragiii, and thefair spacebctween the dia.

ph'ragm and thecorc constituting'atluxpath which, gradually vdecreases' in resistance towards the centerot' the diaphragm.`

jIn anlelectrical receiver7 .incombina' tion, a ycoilloi wire, a sottironcore therefor o'"large..diameter. as compared with Y depth, a large diameter annular` permanent mag`net, andl a diaphragm havingna portion closely Vadgace'nt to saidfcore, and aportioii adjoining.jsaid permanent magnet, and

means for varying the ,space between the diaphragm and the core.

6. In receiver,ran electro-magnet, asinglevhelical permanent magnet, a diaphragm] cooperatingwith said magnets'and arranged adjacent thereto',l so that the entire diaphragmiis utilized uniformly for a magnetic.v iuxipath, (with, thef flux lines all` directed radiallyandot substantially equal intensity at points limited the same distance from the center ot saiddiaphragm.

7. In a receiver, a diaphragm, a coil otV Wire, and a magnetic iluxpath cooperating Withsaid coilrot Wire in, said diapliagin and spaced Jfrom said diaphragm to provide an air gap,"tlie magnetic flux acting onany pointfin thediaphragm beingiproportional to the displacement desired at that point.

In testimony whereof I aiiixiny signature.

DONALD" WV. NORVOOD. 

